The number of knife and offensive weapon offences rose to its highest level since 2010 in the past year, official figures show.

The criminal justice system in England and Wales dealt with 21,381 such offences in the year ending in September, according to the Ministry of Justice, the highest number since the end of September 2010, when the figure was 21,851.

Recent police-recorded crime figures published by the Office for National Statistics showed an increase in the number of knife and offensive weapon offences to 32,986 in the year to June, compared with 18,900 in the year to March 2012.

The figures were published as London’s homicide rate reached its highest level in a decade after another teenager was killed in the capital. The Metropolitan police said officers were called to the fatal stabbing of a teenager in south-east London on Tuesday night, taking the tally to 131, the highest level since 2008 with three weeks of the year still left. The figure includes at least 75 stabbings and 13 shootings.

The Met commissioner, Cressida Dick, said earlier this month that the tide was turning against knife and gun offences, although she admitted it would take more time to tackle the estimated 180 violent gangs in London who drag children into crime, and the root causes of the violence.

In the year to September, 13,477 offences of possessing an article with a blade or point resulted in a conviction or caution in England and Wales. There were also 6,946 cases of individuals found with an offensive weapon and 958 in which a knife or weapon was used to make threats against others.

The Ministry of Justice report said offenders were now more likely to receive a custodial sentence for knife and offensive weapon offences.

In the year to September, 36% of cases resulted in an immediate jail term, and 11% in a caution.

“Custodial sentences are now at the highest level they have been. However, the proportion of offences resulting in a caution is at the lowest level it has ever been,” the report said

Under a “two strikes” system introduced in 2015, minimum sentences were introduced for those aged 16 and over who are convicted of a second or subsequent offence of possession of a knife or offensive weapon. Courts must impose the minimum sentence unless it would not be “in the interests of justice” to do so.

Eighty-two percent of repeat offenders received a custodial sentence in the year to September, with 63% receiving immediate prison terms. The proportion sent straight to prison has risen from around half prior to the introduction of the legislation.

On Thursday, the government will try to frame its funding settlement to policing as being generous. Police chiefs have warned that their forces are being stretched to breaking point, and the home secretary, Sajid Javid, has said he would try to secure more resources from the Treasury.

A spokesperson for the mayor of London said: “This year, we have seen police numbers fall to below 30,000 for the first time in more than a decade and we risk seeing them drop even further with ministers forcing further cuts on the Met police.”